This source category comprises the non-combustion emissions from the production of asphalt in asphalt plants other than refineries and its application (such as paving and roofing operations as well as subsequent releases from the surfaces). It includes asphalt blowing for roofing. The production and use of asphalt results mainly in emissions of NMVOC, CO, SO2 and particulate matter, while the fate of the remaining hydrocarbons are stored in the product (much less than one per cent of the carbon is emitted). Emissions from the installation of roofing materials are assumed negligible. Emissions from the combustion of fuels needed to supply heat to the asphalt processes (production or heating of the asphalt mix) are covered under the Energy Sector.
Asphalt is commonly referred to as bitumen, asphalt cement, or asphalt concrete or road oil and is mainly produced in petroleum refineries. In some countries the laid mixed product is also referred to as 'asphalt' but it also known as 'macadam'. In view of the ambiguities created by differing nomenclatures, a single set of terms will be adopted here and applied uniformly in the text without implying any preferences for the terms used (see Box 5.1).
The heavy black and very viscous organic liquid mainly produced from refineries and used as a feedstock for the road paving and roofing materials will be termed bitumen, to distinguish it from the products made from it. This also conforms to the terminology used in international energy statistics, which may provide some of the data required for emissions estimation. At normal temperatures bitumen is in a semi-solid state. It is processed and used as illustrated in the figure below.
Bitumen ex refinery
Hot Mix Asphalts
The diagram shows that bitumen may be heated and mixed with aggregate of various sizes, diluted with petroleum oils or water/soap emulsions, or heated and blown with air to polymerise/stabilise it and make it suitable for e.g., the treatment of roofing materials. These will be termed 'asphalt processes' and their products will be referred to as 'asphalt products'
Bitumen and aggregates are mixed in either a fixed or mobile plant, usually within 30 to 50 km of the road surface paving site (EAPA, 2003). In industrialised countries typically 80 to 90 percent of bitumen is used for the manufacture of road surface paving (U.S.EPA, 2004). However, in developing countries with rapid infrastructural growth, the amount of bitumen used for roofing products may be of the same order of magnitude as those used for road paving (UNFCCC, 2004). Other uses of asphalt products are as binder or sealant in the production of roofing material, as a foundation sealant, and other industrial uses such as pipe coating.
Direct greenhouse gas emissions, e.g., CO2 or CH4, associated with the production and use of asphalt are negligible since the majority of the light hydrocarbon compounds were extracted during the refining process to produce commercial fuels. From the EMEP/CORINAIR guidebook it can be concluded that CH4 emissions from hot mix asphalt and cutback asphalt and from the asphalt roofing industry are negligible (EEA, 2005). Greenhouse gas emissions from the use of recycled asphalt pavements as aggregate for new road paving are also negligible.
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